Humidity responsive device



Sept. 9, 1941- w. 1., M GRATH HUMIDITY RESPONSIVE DEVICE Filed May 5; 1938 3nventor d ttorneg Patented Sept. 9, 1941 UNITED STATES PATENT OFF-ICE nuiu'mn'r nnsronsrvnnnvlon i William-L McGrath, St. PauLMim, assig nor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn, a corporation ofDelawar-e Application May 5, 1938, sem Nazca! ",3 Claims. (01; 13-335) is responsiveto the vapor pressure or the relative humidity of the atmosphere, andto a device for indicating the vapor pressure or relative humidity of the atmosphere.

One of the objects of the invention is the provision of a novel control device which responds.

I This invention relates to a control device which oi the lever can a tension spring 32 having its other end connected to a suitable adjusting screw 33 whereby the tension of the spring 32 may be varied. It will be seen that the spring 32 biases the bellows IE to its expanded position. Also pivotedat. 3| independently of the lever 30 is an arm 35 provided with a'lug 36 received between rapidly to variations in the vapor pressure or. I relative humidity of the atmosphere and which will'rapidly indicate changes in the-vapor pres: sure or relative humidity of the atmosphere.

Other objects will become apparent upon a-' study or the specification, claims, and appended dehydrating material may be used such for example as silica gel, anhydrous lithium chloride, or calcium'chloride. Suitable sealing means l4 are provided between the enclosure l0 and the cap H to prevent the passage of airtherebetween.

spring members 31 and 38 which are rigidly con- 'nected to the lower end of the lever 30. .These spring members and the lug form a strain release connection between the arm 35 and the lever 30 so that if the arm 35 is not restrained from movement, movement of the lever 30 about its pivot 3i will cause the arm 35 to move therewith. If,

Suitably secured to one wall of the enclosure l3 is an expansible member'which is illustrated as being'in the form of a bellows .l6, theinterior of this'bellows being in communication with the interior of the enclosure ID by means oi.'--the apertime I! in the wall oi the enclosure. The belany suitable mannersuch as by welding, etc., it being understood that the connection between the bellows and the enclosure is air tight. The in- Connected to the outer end of the bellows i3 is an arm 23 pivotally connected at 29 to a lever lows l5 maybe secured to the enclosure 10 in however, the arm'.35 should berestrained from movement the lever 3ll'may still move with respect thereto, one of the spring members 3'! or 38 being flexed and permitting this relative movement of the two members. It will now be seen that if the arm is unrestrained from movement, expansion or-contraction of the bellows It will cause a corresponding movement of the arm 35.

Means in the form of a U-shaped member 43 pivoted at 4| and 42 is provided for normally preventing movement of the arm 35. Rigid with one end 01 the member is a lever 43 which is biased by meansfof a spring 44 in a direction to cause the'member 40 to hold the arm 35 clamped against the plate-45 on which the member 40 is pivoted. It the right end of the lever 43 as viewed in Figure 1 is moved upwardly against the forceof the spring 44, the member 40 is moved in a direction to release the lower end 01' the arm 35 so that it can move with the lever 30.

Means are provided for periodically and alternately opening the valve 22 and releasing the.

arm 35, this means being shown. as including a constantly rotating motor driving a shaft 52 through reduction gearing 53. Mounted on the shaft 52 and cams 54 and 55. The cam 54 includes a cam element 55 which once in every revolution of the cam engages the stem 25 of the valve 22 and causes this valve to move to open position.

The cam 55 includes a cam element 51 which engages the right end oi lever 43 once during every revolution of the cam which raises the member 40 upwardlyout of engagement with the lower end of the arm. spaced apart so. that 'the valve 22 will first be opened and closed and the arm 35'will then be released for movement, these actions taking place 30 which is in turn pivoted at 3| to any suitable periodically and alternately.

surrounding atmosphere to flow intothe recep-- tacle ll through the dehydrating material ll The cam elements 53 and'l'l are which is illustrated as being provided with a plurality ofapertures therethrough, and also around this material and into the bellows l6. Assuming that the atmosphere contains a certain amount of moisture, this moisture will be removed by the dehydrating material I l and if valve 22 is now closed, the removal of the moisture from the atmosphere results in lowering the pressure within the bellows l6 by an amount which is equal to the vapor pressure of the air which has been admitted to the enclosure Ill. Becaus'e'of the great aflinity of the moisture for the dehydrating material II this moisture will be rapidly removed from the air and the pressure within the bellows l6 will rapidly fall, resulting in a contraction of the bellows l6 and movement of the lever 30 in a clockwise direction. Since the arm 35 is at this time prevented from movement by the member 40 the lever so will be moved with respectto the arm 35, this mbvement being permitted by the springs 31 and 38. Sometime after the valve 22 has been opened and closed the cam 55' will cause the release 01! arm'35 for a short time. This arm will now move under the action of the spring 38 until it is oncemore in alignment with the lever 30 and after this movement has taken place the cam 55 will release the lever 43 and the arm 35 will again be clamped in engagement with the plate 45 by the member 40. Aftera predetermined length of time, the valve 22 will again be opened, letting in more air into the enclosure III. This valve will be opened long enough for the pressure within the enclosure Ill and the bellows l6 to become the same as the atmospheric pressure. When this happens the humidity of the air within the enclosure and the bellows will be the same as the humidity of the surrounding atmosphere because of the tendency of the moisture in the air-to rapidly disperse and become equal both within and without the enclosure Ill. If the humidity of the air has varied from the last time that the valve 22 was opened and closed the pressure within the bellows I6 will become diflerent from the last operation .01. the valve since more or less moisture or vapor pressure will be removed by the dehydrating material II and this will be reflected bythe arm 30 assuming a new position. Upon subsequent release of the arm.35 this will also assume a new position corresponding to the new position of the arm 36.

The lower end of the arm 35 may move over a suitable indicating scale 66 from which readings may be taken as to the actual vapor pressure 01' the air. Since the pressure acting on the exterior of the bellows I6 is the total pressure of the air and .since the pressure within the bellows I6 is the total pressurelof the air minus the vapor pressure of the air, the bellows 16 will move in accordance with-variations in the vapor pressure and if the spring 32 isproperly adjusted, readings may ,be taken directly from the scale 60 to give the actual vaporvpressure of the air. The lower endof the arm 35 may be insulated by insulating material 6| and move over a resistance 62 which may ,form the control potentiometer of a pro-.

-portioningmotor 63. This motor maybe of the type illustrated in Patent 2,028,110 issued to D. G. Taylor, January 14, 1936. Conductors 64 and 65 connect the outer ends of the resistance 62 to the outer terminaLs of the motor 63 and acon'ductor 66 connects the lower portion of arm 35 with the center terminal .of the motor 63. An arm is moved by the motor 63 in accordance with the resistance 62 as will be understood from a study of the aforementioned Taylor patent. The-arm 10 may be connected to any suitable-apparatus for varying the relative humidity 01' the space in accordance with the movement of arm 35 so as to properly control the humidity within the space. Any other suitable mechanism may be operated by the arm 35,' the particular mecha-,. nism being controlled by the arm 35 forming no part of the present invention.

The dehydrating material l'l i is so supported within the enclosure ID that it may be readily removed since after an extended period of use sufllcient moisture will have been absorbedby this material that its replacement will be necessary. It will now be seen that a very simple and quicklyresponsive control and indicating device vapor pressure of the air.

has been provided which responds to variations in the vapor pressure of the air and indicates the actual vapor pressure of the air. In the event that the vapor pressure of the air remains constant for an extended period of time'the arm 35 will not 'move although the arm 30 will be moved each time the valve 22 is opened since the pressure within the bellows will be built up to the atmospheric pressure and will again drop to the pressure which is the atmospheric pressure less the vapor pressure. Since the arm 35 is not released for movement until the pressure within the bellows has returned to the atmospheric pres,- sureless the vapor pressure, it the vapor pressure remains constant the arm 33 will be in the same positionevery time that the arm 35 is released for movement so that while thearm' 30 will be constantly moved back. andforth the arm 35 will move only when actual changes in the vapor pressure of the air occur. 5 Referring now to Figure 2 the apparatus disclosed is similar to Figure 1 except for the provision of means acting on the lever 30 so that this leverwillmove in accordance with the relative humidity in the space. The spring 32 is now replaced by a spring 15 which acts in the opposite direction from the spring 32, or in other words, tends to cause collapse of the bellows l6. This spring maybe connected-to a suitable adjusting screw 16 whereby its tension may be varied. A bellows 80 is suitably supported at one end and is provided with a pin or like member 8| rigidly connected thereto at the other end of the bellows and engaging the lever 30 below the pivot 3|. This bellows is partially filled with water and it will be apparent thatthe air. within the bellows 80 will be in a saturated condition. The pres sure exerted by the bellows 80 against the lever 30, which pressure tends to expand the bellows l6, will be a pressure which is equal to the saturated vapor pressure oi the air at the particular temperature of the air at any time. Acting against the exterior .of both of the bellows l6 and 80 is atmospheric pressure and if the bellows are of equal size the efi'ect of this atmospheric pres sure on one bellows will be counteracted by the eflect oi the pressure on the other bellows. in Figure 1 there will be a force tending to col-; lapse the bellows l6 which is equal to the actual There will be a force tending to expand this bellows which is exerted by the bellows 80 and which is equal to the saturated vapor pressure of the air so that the arm 35 will actually be moved in accordance with varthe saturated vaporpressure of the air. If now movement of the lower-end of arm 35 over the the spring 15 is properly t i thisg-rm' 'wnl 9 9 which meshes with the rack 91.

move in accordance with variations in relative humidity of the air and this relative humidity can be directly read from the scale 95 over which the lower ends of the arm 35 moves. Suitable control apparatus may also be operated by the control element 35 as in Figure 1 but since this particular control apparatus forms no part of. the present invention it is not being illustrated.

Referring now to Figure 3, a very simple arrangement for indicating the actual vapor pressure of the air is illustrated. An enclosure 99 has suitably supported therein as by means or a cap 9| threaded into the bottom of the enclosure, suitable dehydrating, material 92. Air is periodically admitted into the enclosure by means of a hand operated valve 99 which is normally biased.

closed by means of a spring 94. Communicating with the interior of the enclosure is a Bourdon tube 96 which is connected by means of a rack 91 to an indicating arm 98 provided with a gear The action of this type of tube is well known and in response to an increase in the internal pressure within the tube, the tube tends to straighten out so that the rack 91 is moved toward the'left causing movement of the indicating arm 98 to the left. Conversely upon a decrease in the pressure or the'tube 9c the arm as will be moved toward' the right. It will now be understood that every time air is admitted by means of the valve 99 into the enclosure 99 and the valve then closed, the pressure within the enclosure 90 and the Bourdon tube 96 will be reduced by the vapor pressure 01 the air since the vapor is removed by the dehydrating material 92 and since the pressure acting exterlorly on the tube 98 is the total pressure of the air, the indicating arm 98 will actually move in accordance with variations in the vapor pressure and the scale I99 over which the pointer 99 moves may be graduated so as to indicate directly the actual vapor pressure oi the air.

It will-now be seen that with the device of Figure 3, whenever it is desired to determine the vapor pressure or the air it is necessary only to manually operate the valve 93 and within a comparatively short period of time the pointer 98 Having described theprei'erred forms of my invention many modifications may become apparent to those skilled in the art and it should be understood that the invention is limited only by the scope of the appended claims.

I claim as my invention:

1. In a controller of the class described, an enclosure, an expansible member communicating with said enclosure, normally closed valve means for controlling the admission of air to said enclosure, a control element, means including a strain release device for operatively connecting said expansible member and said control element, means normally preventing said control element from moving. in response to movement of said expansible member, means for supporting a dehydrating material in said enclosure, and

means for alternately opening said valve means of the air biasing said expansible member to expanded position.

3. In a device of the character described, an

enclosure for receiving a dehydrating material, said enclosure including an expansible portion,

'means for controllably admitting air to said enclosure, an element operatively connected to said expansible portion and movable thereby, and means responsive to a saturated vapor pressure of the air biasing said expansible member to expanded position.

WILLIAM L. MCGRATH. 

